JP4193220B2 - Audio meter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an audio meter device, and in particular, in a digital audio device such as a digital mixer, a digital tape recorder, and a digital VTR, an audio that can realize both a VU meter function and a peak meter function using one display device. It relates to a meter device.
[0002]
[Prior art]
Conventionally, in an audio device in which a signal is processed in an analog manner, even if the signal level exceeds the maximum allowable level, the linearity is somewhat impaired, and a large distortion does not occur immediately. However, in a digital audio device such as a digital mixer, a digital tape recorder, or a digital VTR, a large distortion occurs when the signal overflows, so that the signal level does not exceed the maximum permissible level in the device even for a moment. This is very important.
[0003]
For these reasons, as a general method for visually monitoring the amplitude level of an audio signal, analog audio equipment has often used a VU meter that can approximately display the volume received in the sense of hearing. On the other hand, peak meters capable of monitoring the maximum signal level have been used in digital audio equipment.
[0004]
However, the conventional digital audio equipment having a peak meter can monitor the maximum permissible level, but has a problem that it cannot monitor the sense of volume that is actually heard. Therefore, for example, a method of D / A converting a digital signal and simultaneously monitoring it with an analog VU meter has been proposed. FIG. 7 is a front view showing an example of a level display device in a conventional digital audio device. In this example, a digital display peak meter 60 and an analog display VU meter 61 are provided. For example, Japanese Utility Model Laid-Open No. 55-155911 discloses a technique for associating the arrangement of a VU meter and a peak meter. As another related known document, for example, Japanese Patent Application Laid-Open No. 5-275945 discloses a level display device that displays a reference level together with an output level.
[0005]
[Problems to be solved by the invention]
In the conventional level display system as described above, two display devices are required, which increases the amount of hardware, makes it difficult to reduce the size of the device, and increases the cost.
An object of the present invention is to solve the above-described problems of the prior art and to provide an audio meter device capable of realizing both a VU meter function and a peak meter function using a single display device. is there.
[0006]
[Means for Solving the Problems]
In the audio meter device, the present invention displays both the means for detecting overflow of the input signal, the means for filtering the input signal with the characteristics of the VU meter, the output information of the filter means for the VU meter and the output information of the overflow detecting means. Display means.
In the present invention, both the VU meter function and the peak meter function can be realized by using an existing display device, and the display of the VU meter and the monitoring of the overflow can be realized at the same time.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a perspective view showing the structure of the digital mixer device 18 equipped with the audio meter device of the present invention. The digital mixer device 18 is roughly divided into three parts. The operation panel 10 is equipped with, for example, a fader 11 for each channel, a switch 12 for performing connection control, a volume 13 for adjusting the depth of various acoustic effects, and the like, and a display changeover switch 14 related to the present invention. It is equipped with 15 mag.
[0008]
The display panel 16 is also equipped with the display device 17 of the audio meter device of the present invention for each channel. A processor rack having a CPU, a DSP (digital signal processor), etc., which will be described later, is built in the main body 18 and is connected to an external device via an input / output connector panel arranged on the back surface 19. Yes.
[0009]
FIG. 1 is a front view showing configurations of a display unit (a) and an operation unit (b) of an audio meter device to which the present invention is applied. A large number of display devices 1 (17) arranged on the display panel 16 are display devices using display elements such as LEDs (light emitting diodes) or fluorescent display tubes, and 0 dB is input by inputting display digital data. The level up to -∞ dB can be displayed in decibels. There is also an overflow display at the top that indicates that the data has overflowed the maximum allowable level.
[0010]
The display changeover switches 2 (15) and 3 (14) arranged on the operation panel 10 of the operation unit (b) are switches for causing the display device 1 to display the peak level or the VU level by operating each of them. It is. Each of the switches 2 and 3 has a built-in indicator such as an LED or a lamp, and displays a selected state. FIG. 1 (b) shows that the peak meter is currently selected. Note that the switches 2 and 3 may be mechanical lock type switches in which one of them is released when the other is pressed, or a simple push button switch is used, and the CPU changes the display state by detecting one of the presses. In addition, the switch indicator may be driven.
[0011]
FIG. 3 is a block diagram showing a circuit configuration example of a digital mixer device equipped with the audio meter device of the present invention. The circuit is roughly divided into two blocks, and the signal processing unit in the upper part of FIG. 3 includes a plurality of DSPs and adders. Serial digital signals input from a plurality of signal input terminals are input to the corresponding DSPs 20 and 21, respectively. The DSPs in FIG. 3 are all the same and have serial ports for signal input / output and control. In the DSPs 20 and 21, for example, fader (level adjustment) processing is performed on the signals based on the control of the CPU 30 described later.
[0012]
The serial output signals of the DSPs 20 and 21 are respectively input to the next-stage DSPs 22 and 23. In these DSPs, for example, an equalizer process or a sound effect process is performed. The output signals of the DSPs 22 and 23 are input to the adder 24. The adder 24 generates a plurality of output signals, for example, L and R channels, by selecting and adding / combining signals of a desired channel. A plurality of output signals of the adder 24 are input to the DSPs 25 and 26, and for example, fader processing of the output signals is performed. The output signals of the DSPs 25 and 26 are respectively input to the DSPs 27 and 28, and the DSPs 27 and 28 perform meter processing related to the present invention described later.
[0013]
The control unit in the lower part of FIG. 3 includes a CPU 30 and its peripheral circuits, and controls the entire mixer apparatus. The CPU 30 reads operation information from the panel circuit 32 of the operation panel 10 based on a program stored in the memory 31, controls the signal processing unit described above, and selects a desired display device 36 on the display panel 16. It is the processing device which displays the information.
[0014]
The memory 31 includes, for example, a ROM storing programs and a RAM used as a work area. The panel circuit 32 generates state information of various operators of the operation panel such as the fader 11, the switch 12, and the volume 13. The CPU 30 reads the state information of the panel circuit 32 via the PIO (parallel input / output circuit) 33 and the bus 37.
[0015]
The SIO (serial input / output circuit) 34 has a plurality of serial ports, and the CPU 30 reads necessary information from each DSP via the SIO 34, and sends control information such as fader information and channel selection information to the DSP and adder. Write. The display device 36 includes a plurality of display devices 1 and their drive circuits as shown in FIGS. 1 and 2, and the CPU 30 transfers display data to the drive circuit via the PIO 35 to drive the display device 36.
[0016]
FIG. 4 is a functional block diagram showing circuit functions of the digital mixer device. The faders 40 and 41 adjust the signal level for each channel based on the position information of the fader controls on the operation panel 10. This function is realized by, for example, the DSPs 20 and 21, and is implemented by multiplying the input signal data by a fader coefficient in the range of 0 to 1 set by the CPU 30. The equalizers (EQ) 42 and 43 are realized by, for example, the DSPs 22 and 23, and are implemented by, for example, IIR filter processing having characteristics set by the CPU 30.
[0017]
The signal adder 44 is a signal synthesizer that independently generates a plurality of output signals by selecting and adding signals of a desired channel, and FIG. 4 describes a configuration in which signals are synthesized by a bus. However, this represents a function in the form of an analog signal, and actually includes a multi-input adder 24 as shown in FIG.
[0018]
The faders 45 and 46 are parts for adjusting the output signal level, and are realized by the DSPs 25 and 26, for example. The meter processing units 47 and 48 are parts for generating display data of the audio meter device according to the present invention, and are implemented by the DSPs 27 and 28, for example.
[0019]
FIG. 5 is a functional block diagram showing the internal configuration of the meter processing units 47 and 48 in FIG. The signal data input to the signal input terminal “Meter IN” is output to the signal output terminal “Meter OUT” as it is, and also input to the overflow detection unit 50 and the changeover switch. The overflow detection unit 50 outputs “1” as an overflow indication bit when the absolute value of the input data value exceeds the maximum allowable level.
[0020]
The changeover switch connects (transfers) the input signal data to the filter unit corresponding to the currently selected display format based on the status information of the display changeover switches 2 and 3 on the operation panel 10. The VU meter filter unit 51 is constituted by, for example, an IIR filter, and filters a signal with characteristics approximate to the display characteristics of a conventional VU meter. That is, it functions as a low-pass filter having a time constant of about several hundred milliseconds at both the rising and falling portions of the signal.
[0021]
On the other hand, the peak meter filter unit 52 is also constituted by an IIR filter, but reacts quickly so that the output level follows the input signal almost in real time at the rising portion of the signal, and at the falling portion. The filter functions as a low-pass filter having a time constant of several hundred milliseconds or more so that the user can easily recognize the peak value.
[0022]
The meter value output unit 53 selects and reads out the output display data of the filter unit corresponding to the currently selected display format based on the read command from the CPU 30, and transfers it to the CPU 30 together with the overflow display bit. Note that once an overflow indication bit is set, the meter value output unit 53 holds the bit until it is read by the CPU 30 and is not cleared.
[0023]
FIG. 6 is a flowchart showing the contents of meter processing in the CPU 30. This program is activated at a predetermined cycle. In S1, the state of the display changeover switches 14 and 15 on the operation panel 10 is read. In S2, whether the VU meter display or the peak meter display is determined based on the read state information of the switches 14 and 15, and the state information is transferred to the DSPs 27 and 28 that perform meter processing via the control serial port. . Based on the set information, the DSP executes meter processing in a functional block as shown in FIG. 5 to generate a meter value.
[0024]
The processes after S3 are executed independently for each meter, but only the process corresponding to one meter is shown in the flowchart. In S3, the CPU 30 transmits a meter value transfer request command to the DSP, and the DSP that has received the command transmits the meter value to the CPU 30. The CPU 30 receives the meter value via the SIO 34. In S4, it is determined whether or not the overflow indication bit of the received meter value is “1”. If the determination result is affirmative, the process proceeds to S5.
[0025]
In S5, in order to make it easy for the user to recognize the overflow display, a timer for lighting the overflow display continuously for 3 seconds, for example, is set (started) when it overflows even for a moment. In S6, display data to be set in the driver circuit of the display device is generated. As the level data in the display data, for example, table conversion or the like is performed based on the level data in the read meter value to obtain data corresponding to each display bit of the display device. The overflow display bit is “1” if the timer of S5 is in operation, and “0” if it is stopped. In S7, the generated display data is output to the driver circuit of the corresponding display device via the PIO 35.
[0026]
The audio meter device of the present invention can realize both the VU meter function and the peak meter function by using only one existing display device by the configuration and operation as described above, and displays the VU meter. And overflow display can be performed simultaneously.
[0027]
Although the embodiments have been disclosed above, the following modifications are also conceivable. 3 and 4 disclose an example in which an audio meter is provided only for each output channel. For example, a DSP for performing meter processing is provided between the DSPs 22 and 23 and the adder 24 in FIG. By inserting, it is possible to easily implement an audio meter corresponding to each input channel. In the embodiment, an example has been disclosed in which each DSP performs a single function, but a single DSP may execute processing for a plurality of functions or a plurality of channels.
[0028]
Although an example in which an audio meter is provided in a digital mixer device has been disclosed as an embodiment, for example, when the mixer device is connected to a device that inputs and outputs with analog signals, an A / D converter or D is connected to the input / output terminal. A / A converter may be provided.
[0029]
As an embodiment, an example in which an audio meter is installed in a digital mixer device has been disclosed. However, the audio meter of the present invention includes any digital audio such as a digital mixer, a digital tape recorder, a digital VTR, a CD player, a DAT, and a DVD player. Applicable to equipment.
[0030]
【The invention's effect】
As described above, in the present invention, both the VU meter function and the peak meter function can be realized by using one display device, and the display of the VU meter and the overflow monitoring can be realized at the same time. There is an effect that can be. In addition, there is an effect that the amount of hardware is reduced as compared with the conventional device, the device can be downsized, and the cost is also reduced.
[Brief description of the drawings]
FIG. 1 is a front view showing a configuration of a display unit (a) and an operation unit (b) of an audio meter device to which the present invention is applied.
FIG. 2 is a perspective view showing the structure of a digital mixer device 18 equipped with an audio meter device of the present invention.
FIG. 3 is a block diagram showing a circuit configuration example of a digital mixer device equipped with the audio meter device of the present invention.
FIG. 4 is a functional block diagram showing circuit functions of the digital mixer device.
FIG. 5 is a functional block diagram showing an internal configuration of a meter processing unit.
FIG. 6 is a flowchart showing the contents of meter processing of a CPU.
FIG. 7 is a front view showing an example of a level display device in a conventional audio device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,17 ... Display apparatus 2, 3, 14, 15 ... Display changeover switch, 10 ... Operation panel, 11 ... Fader, 12 ... Switch, 13 ... Volume, 16 ... Display panel, 18 ... Digital mixer apparatus, 19 ... Back Panel, 20, 21, 22, 23, 25, 26, 27, 28 ... DSP, 24 ... Adder, 30 ... CPU, 31 ... Memory, 32 ... Panel circuit, 33, 35 ... PIO, 34 ... SIO, 36 ... Display device, 37 ... Bus

Claims (3)

Overflow detection means for detecting an overflow of the input signal;
VU meter filter means for filtering an input signal according to the characteristics of the VU meter;
An audio meter device including display means for displaying both output information of the VU meter filter means and output information of the overflow detection means ,
A timer that starts when the overflow detection means detects an overflow;
An audio meter device that performs overflow display continuously for a predetermined period of time when the timer is started . Overflow detection means for detecting an overflow of the input signal;
VU meter filter means for filtering an input signal according to the characteristics of the VU meter;
Filter means for the peak meter for filtering the input signal by the characteristics of the peak meter;
Selection information input means;
Display means;
According to the selection information input by the selection information input means, one of the output information of the VU meter filter means and the peak meter filter means is selected and output to the display means together with the output information of the overflow detection means. An audio meter device including display information selection means ,
A timer that starts when the overflow detection means detects an overflow;
An audio meter device that performs overflow display continuously for a predetermined period of time when the timer is started . Input signal is a digital signal, said overflow detection means, the VU meter filter means, audio according to claim 2, wherein the filter means and the display information selection means for the peak meter that is configured by a DSP Meter device.

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